Orientadora: Profa. Dra. Paula Toshimi Matumoto Pintro

Data da Defesa: 20/02/2020

INTRODUCTION. The Myrtaceae family has several species that present bioactive compounds and antioxidant activity through fruits and leaves. Eugenia pyriformis Cambess is a species belonging to the Myrtaceae family and it can be called uvaia, uvaieira, uvaiado- campo, uvalha e uvalha-do-campo, can reach a height of 15 meters, has edible fruits, piriform and succulent, the coloration can range from yellow to orange and have 2 to 2.4 cm of diameter. Different bioactive compounds are found in leaves and fruits of uvaia. Natural antioxidants are targets of consumer interest, due to their potential nutritional and therapeutic effects. Besides being part in endogenous plant defense, antioxidants are also known to have beneficial effects on pathological events. The consumption of minimally processed fruits has been growing all over the world, however when this type of product is processed, certain changes may occur. In the fresh-cut apple one of the changes is the enzymatic browning caused by polyphenol oxidase. Some techniques such as the use of edible coatings added with anti-browning compounds can contribute to the maintenance of the quality of this product.
AIM. The aim of this study was characterize the extract of Eugenia pyriformis Cambess leaf and evaluate the effect of sodium alginate edible coating formulated with leaf extract on the enzymatic browning of fresh-cut apples (cv. Golden Delicious and Royal Gala).
MATERIAL AND METHODS. Uvaia leaves (Eugenia pyriformis Cambess) were obtained from a rural property in the city of Sarandi - PR (23 ° 27 '8' S, 51 ° 51' 10 '' W). The apples were obtained from the local market. The leaves were sanitized, oven dried and ground to prepare the methanolic and aqueous extract. The extract was characterized through the total polyphenols content (TPC) and total flavonoids content (TFC), antioxidant activity (ABTS IC50), high performance liquid chromatography and inhibition of polyphenol oxidase activity. Sodium alginate edible coating was prepared using 1.5% sodium alginate (w/v) and 1% glycerin (w/v), to the treatment was added 2% aqueous extract of E. pyriformis Cambess leaves. Edible coating was characterized by analysis of antioxidant activity, microstructure and x-ray diffraction. Apples were sanitized, cut and applied the edible coating. During eight days of storage the browning index, weight loss and activity of the polyphenol oxidase enzyme of each cultivar were analyzed.
RESULTS AND DISCUSSION. The aqueous extract of E. pyriformis Cambess (EPA) leaf showed 76.03 mg GAE/g dw for TPC, 3.25 mg QE/g dw for TFC, 0.77 mg/mL for ABTS IC50. The methanolic extract of E. pyriformis Cambess leaf (EPM) presented 173.00 mg GAE/g dw for TPC, 11.60 mg QE/g dw for TFC, 1.05 mg/mL for ABTS IC50. Enzyme inhibition was evaluated for Golden Delicious (GD) and Royal Gala (RG) cultivar, EPA showed 80% inhibition for GD and 92.90% inhibition for RG, EPM showed 73.30% of inhibition for GD and 82.40% for RG. High performance liquid chromatography analysis identified peaks that may indicate the presence of chlorogenic acid, caffeic acid and pcoumaric acid. Edible coating had an increase of 16% in antioxidant activity when EPA was added, and by scanning electron microscopy analysis it was possible to identify the good coating homogeneously on the apple. X-ray diffraction confirmed no structural differences between the two coatings. GD apple presented 5.60 UE/min for enzymatic activity, while RG presented 3.50 UE/min. Using the edible coating the browning index was reduced for both apple cultivars, and for GD the edible coating with EPA was more efficient, for RG no significant difference was found for the browning index when compared to the edible coating without EPA and with EPA.
CONCLUSION. Eugenia pyriformis leaf extract can be used as a source of bioactive compounds, presenting antioxidant activity and inhibition of the polyphenol oxidase enzyme. For the minimally processed Royal Gala apple only the edible coating without the extract was sufficient to control enzymatic browning. For the minimally processed Golden Delicious, the use of E. pyriformis leaf extract edible coating showed the greatest reduction in enzymatic browning.
Keywords: Bioactive compounds, minimally processed, polyphenol oxidase, sodium alginate.

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